When battling a cold or the flu, you may notice that your skin feels unusually tender, achy, or painful, even to a light touch. This heightened skin sensitivity is a normal biological reaction to illness. The feeling can range from a mild, all-over soreness to a sensation similar to having a sunburn, which makes clothing or sheets feel irritating. This temporary change in how your skin processes sensation is a direct consequence of your immune system activating its defenses against an infection.
The Body’s Systemic Inflammatory Response
When the body encounters a pathogen, the immune system initiates systemic inflammation. This response involves the release of specialized chemical messengers called cytokines into the bloodstream. Cytokines, such as interleukins and interferons, coordinate the fight against the infection throughout the body. These circulating chemicals are responsible for the general malaise associated with being sick, including fatigue and widespread body aches. They act on the brain to promote sleep and loss of appetite, which helps conserve energy for the immune response. These inflammatory mediators circulate systemically, affecting tissues throughout the entire body, including the skin.
How Immune Messengers Activate Skin Nerves
The systemic inflammatory response creates a direct link between the immune system and the skin’s sensory network. Cytokines released into the blood travel to the skin, where they interact with peripheral nerve endings, known as nociceptors. These nerve endings are responsible for sensing pain, potential harm, and temperature changes. The interaction of these chemical mediators causes neuronal sensitization, which lowers the threshold at which the nerves fire a pain signal to the brain. Nociceptors become hyper-responsive, reacting intensely to stimuli normally perceived as harmless touch or mild pressure. This heightened nerve sensitivity manifests as hyperalgesia (increased sensitivity to painful stimuli) and allodynia (the experience of pain from non-painful stimuli, such as the gentle pressure of clothing or a blanket). This chemical-induced over-sensitization explains why your skin feels sore and tender when you are ill.
Physical Factors That Worsen Skin Discomfort
While the chemical changes are the primary cause of skin discomfort, other physical factors related to illness can intensify the sensation. Fever, a common sign that the body is actively fighting an infection, causes fluctuations in core body temperature. This process increases blood flow to the skin’s surface, which can lead to feelings of warmth or flushing and make the skin sensitive to external temperature changes. Illness often results in a reduced intake of fluids and can be accompanied by increased fluid loss through fever-induced sweating, leading to mild dehydration. When the body is dehydrated, the skin’s barrier function is compromised, and it can lose its natural moisture, becoming tight, dry, and more irritable. This dryness exacerbates the already heightened nerve sensitivity, contributing further to overall skin discomfort. Additionally, the body may redirect blood flow as part of the fight against the pathogen, which can sometimes contribute to the feeling of flushed or irritated skin.